Estrategias analíticas para la monitorización de sustancias inhibidoras de los procesos biológicos implicados en el tratamiento de aguas residuales

Abstract

The water growing overexploitation and pollution have led to the proposal of strict water management and control measures. In this context, wastewater treatment plants play a fundamental role in the circular economy of water and in the elimination of pollutants that are dangerous to health and the environment. However, the presence of some toxic substances can inhibit the biological treatment processes of wastewater and, thus, negatively affect the performance of WWTPs. Therefore, for the correct operation of the treatment plants, a rigorous control of these substances is necessary, which, in turn, requires new analytical strategies that allow a more efficient monitoring of the contaminants. This means proposing methodologies more in line with the characteristics of the analytes and the complexity of the samples. Since the current trend is aimed at developing miniaturized and sustainable methods, the development of automated and portable systems is of great interest, because they allow to propose fast, precise, economical and safe methods. In this doctoral thesis, different analytical methods have been developed for the monitoring of inhibitory substances in biological wastewater treatment. The proposed methods are divided into automated systems based on flow analysis techniques and portable systems that integrate 3D-printed devices. In the first two works, automated methods of dispersive liquid-liquid microextraction with magnetic stirring assisted in a syringe (in-syringe-MSA-DLLME) have been developed for the extraction and preconcentration of volatile fatty acids and long-chain fatty acids. The proposed methods have allowed the injection of a clean extract in the gas chromatograph, avoiding the problems of direct aqueous injection. Under optimized conditions, the methods have been applied in the analysis of wastewater samples and anaerobic reactors. In the third work, a method based on paper sensors and a 3D-printed portable colorimetric system is carried out for the determination of ammonia and sulfide in anaerobic digesters and wastewater. The paper sensors have been impregnated with a bromothymol blue indicator and with the methylene blue method reagents for the detection of ammonia and sulfide, respectively. The procedure, based on the pervaporation of gaseous analytes in a microplate, has allowed the multiparameter analysis of samples with complex matrices. The method proposes a rapid colorimetric analysis of images captured with a smartphone. Abstract xvii In the fourth work a method has been developed to analyze iron in the field. The method includes a miniaturized spectrophotometric system with 3D-printed supports and a simple procedure for solid phase extraction of iron. Fe (III) has been preconcentrated with a small column and determined as Fe (II) with the phenanthroline method. The optimized method has been applied in the analysis of different water samples, including a sample from a biodigester. The proposed method is committed to the sensitive determination of iron in the field without the need to use expensive instruments. In the fifth and last work, a portable platform for the in-situ extraction of phenolic contaminants in wastewater and biodigesters samples is proposed. The platform integrates a 3D-printed stirrer with paddles coated with the metal-organic network MIL-100(Fe) for the extraction and pre-concentration of analytes. The stirrer paddles are removable and can be taken to the laboratory for HPLC-DAD analysis. The proposed platform allows the integration of the sampling and the extraction of the analytes in a single step.